Paper feed device



y 1966 J. G- MOXNESS 3,260,521

PAPER FEED DEVICE Filed Aug. 12, 1965 INVENTOR. -1 55/1 15 dMax/vfss United States Patent 3,260,521 PAPER FEED DEVICE James G. Moxness, North St. Paul, Minn., assignor to Minnesota Mining and Manufacturing Company, St. Paul, Minn., a corporation of Delaware Filed Aug. 12, 1963, Ser. No. 301,340 4 Claims. (Cl. 271-39) This invention relates to devices for separating and feeding sheet-type articles from a stack, particularly to feeding mechanisms associated with duplicating equipment.

A desirable feature in feeding mechanisms of duplicating machines, printing presses, data processing equipment and the like is that they separate and advance a single sheet or card only from the stacked supply of paper or cards. Mechanisms using vacuum to lift and advance the top sheet of the stack have been most successful in accomplishing exact feeding, but these vacuum pickup devices are too large and expensive for many purposes. Other known methods are deficient also for reasons of size or expense or because they lack accuracy or simplicity in arrangement, or damage the material fed. Such methods include urging the leading edge of top sheets in the stack against a rough surface which separates the edges and thus usually the sheets, or feeding the sheets through a plurality of fixed stops or between rollers turning in opposite directions.

A feeding mechanism embodying the present invention has been found to have a high accuracy, though of much simpler design than vacuum devices. In addition, the novel feeding mechanism may be used to separate from a stack and feed unattached multi-sheet units, when there are at least two sheets in the unit of different frictional characteristics. The device also has the advantages of inexpensiveness and small size, and is easily included as an element of duplicating or other equipment.

In a preferred embodiment the novel feeding mechanism includes a support frame, a drive roller rotatably fixed to the frame, and movable support means for a stack of sheets of paper or cards attached to the frame and biased toward tangency with the drive roller. An end of the support means is adjacent the drive roller to urge the leading edge of an outside article of the stack tangentially against the drive roller. A movable stop is also biased against the drive roller adjacent said end of the support means and is mounted by means attached to the frame on the same side as the stop of a line substantially parallel to and slightly spaced in the direction :of the roller from the path of feed from the stack. A portion of the surface of the stop adjoining the area of abutment of the stop with the roller is inclined away from the roller toward the support means so that, under pressure of an article engaged by the drive roller and moved against the inclined surface, the stop is moved away from the roller and the article permitted to advance.

In the following description the above features will be more explicitly described in terms of illustrative but nonlimitative examples and in connection with the appended drawing, in which:

FIGURE 1 is a schematic side elevation, partly cut away, of the feeding mechanism;

FIGURE 2 is a schematic front elevation of the feeding mechanism, and

FIGURE 3 is an enlarged schematic elevation of a portion of the mechanism shown in FIGURE 1.

The mechanism shown schematically in FIGURES 1 and 2 includes a simplified frame 10 on which is pivotally mounted at 11 one end of a support table 12. The other end of the table 12 is free to be depressed when the table is loaded with a stack 13 of paper sheets, cards, etc., against the force of a pair of springs 14. A drive roller 15 is rotatably supported away from the free end of the table 12 so that the roller is engaged by the leading edge of the outside article in the stack under the force of the springs 14. The roller 15 is turned, by means not shown, in the direction indicated to apply a force in the plane of the outside of the stack tending to advance both the outside sheet and, through the friction existing between the sheets, the sheets underneath.

A blade-like stop 16 abuts and extends generally radially from the roller 15 as a barrier to the passage of sheets from the stack. The stop is carried by support arms 18 pivoted to the frame 10 at 19, and springs 20 attached between the frame 10 and arms 18 urge the stop against the roller. The abutting edge of the blade-like stop 15 is beveled to provide a surface 21 facing the stack 13 that is inclined away from the roller 15 and against which the roller drives the top sheets of the stack. The extent of the surface 21 must be such that the lower edge of at least one sheet of a paper whose use is contemplated with the feeding mechanism will strike the incline, force away the stop, and be fed between the stop and roller. Normally several of the outside sheets in the stack will contact the incline at one time.

If the sheets of the stack are identical, or have surfaces with substantially the same frictional character, only one sheet will be fed past the stop. This will be true substantially independently of the force by which the stop is held against the roller 15 so long as that force is not so great as to prevent any sheet from passing the stop. Of the sheets lettered A, B, and C in FIGURE 3, sheet B will be acted on by two counter forces-the frictional force of sheet A acting to move sheet B and the almost equal opposite frictional force of sheet C acting to restrain sheet B from moving. Thus, a very small bias on the stop 16 will overcome the difference in the two frictional forces by the sheets A and C on sheet B and prevent sheet B from moving. Because of the large difference between the force of the roller on sheet A and the frictional force of sheet B on sheet A, sheet A will depress even a fairly strongly biased stop 16 provided that the forces involved are not so large as to crumple or tear the paper. In the illustrated embodiment, the roller 15 is driven one turn periodically, advancing a sheet to a position where the sheet is engaged by a set of rollers which draw the sheet completely from the stack. When not driven, the roller 15 freely rotates under the pull of the sheet that is being further advanced.

Under the right conditions two or more different sheets can be fed past the stop at one time as a package or unit." If the friction between sheets B and C is substantially less than that between A and B, for example because either the bottom surface of B or the top surface of C is smoother than the corresponding surface between sheets A and B, the net force on sheet B by sheets A and C will overcome a moderately biased stop 16 and permit both sheets A and B to advance together past the stop. The number of sheets fed each time is determined by the spacing through the stack 13 of the low-friction interfaces. A typical occasion for simultaneously feeding two sheets is a printing or duplicating operation in which slip sheets are used as a barrier against the transfer of chemicals, ink, heat, etc., between treated or printed sheets.

The top of the stop 16 might be formed with a sharp edge instead of the flat portion shown in FIGURE 3 as in contact with the roll 15, but a stop with a flat edge portion as illustrated is more easily manufactured, since it is difi'lcult to machine a fine edge that is even and free from burrs. The narrow flat surface is also less likely to be changed by the continued withdrawal of the sheets from stack 13 than is a sharp edge. The rear bevel on the stop is provided as a means of more carefully dimensioning the width of the flat portion, which preferably is kept small so as to decrease the tendency for a second sheet to be pinched between the roller and stop behind the trailing edge of the advanced sheet. The angle by which the surface 21 is inclined to the path of feed has been found not especially critical, though angles in the neighborhood of 45 are normally selected. The surface 21 should be free of nicks and burrs and preferably is chrome or nickel plated. The roller has a roughened surface and is moderately soft, though softness is not especially critical. Rollers may, in fact, be made of a material such as metal provided the proper frictional relationship between the roller surface and the sheet surface be maintained. Roughening of the roller surface is one Way in which the frictional forces between roller and sheet may be increased.

It has been found that placing the connection 19 of the support arm 18 to the frame substantially above the top of the stop 16 introduces an unpredictable vertical force on the stop 16 forcing the stop into the roller 15. This vertical force is a component of that force on the stop that occurs in reaction to the force of the roller on the stop. Since the reaction force is angled toward the pivot connection 19 of the stop to the frame, it has a vertical component which may vary depending on the dimensions of a particular machine to cause undesirable effects. If the connection 19 is only slightly above or below the top of the stop, the vertical component is small enough or directed away from the roller so as not to raise problems. Other means of supporting the stop have been used, such as guides between which the side edges of the stop slides, with a spring biasing the stop upwardly. The spring pressures may be changed by screw adjustment means, not shown, or by substituting springs according to the type of paper with which the feeding mechanism is to be used, lighter pressures being used for thinner papers.

Instead of using a drive roller to advance the top sheets, other conventional drive mechanisms, such as reciprocating, rubber-tipped fingers, might, of course, also be used. A fixed upper guide member against which a stop 16 abuts might then, or also for other reasons, be substituted for the roller, which in the illustrated embodiment serves the double function of drive means and guide cooperating with the stop to define a feed passage. It will also be seen that the invention may be applied to devices which feed from the bottom of a stack as well as those that feed from the top. A further conventional design of paper feeding devices which permits use of the invention is a mechanism in which the drive roller 15, and in the present case the stop 16, are movable, e.g. by gravity, against the stack, rather than the support table 12 being movable.

In a specific structure based on the schematic design illustrated and intended for 8 /2 x 11 inch sheets of paper having a thickness in the range of 3-8 mils, the vertically disposed stop was 1.25 high, 0.065 thick, and 9.5"

long and was pivoted about a point 2.0" from the stop and 0.75" below the top of the stop. The surface 21 of the stop was inclined at an angle of 45 from the vertical with the lower edge of the surface 21 being 0.025" below the top of the stop; the level portion at the top of the stop was 0.015" wide. The roller, made of natural rubber with a durometer measurement of 40, had a diameter of 1.25" and a length of 4". The springs 14 held the stack against the roller with a force of 4.8 lbs. for the largest stack and a force of 2 lbs. when just a few sheets were on the table, while the springs 20 biased the stop against the roller with a force of 3 lbs.

What is claimed is as follows:

1. A device for separating and feeding sheet-type articles from a stack comprising a frame, a drive roller rotatably fixed to the frame, vertically movable support means for the stack attached to the frame, an end of the support means being positioned beneath and biased toward the drive roller to urge the leading edge ofthe topmost article of the stack tangentially against the bottom of the drive roller, and a stop resiliently biased into contact with the bottom of the drive roller adjacent said end of the support means, movable from the roller in a direction angled to the path of feed, and supported by a pair of arms pivotally attached to the frame below a level slightly above the top of the stop, the surface of the top of the stop including a portion adjoining the area of abutment inclined away from the roller toward the support means and angled across the path of feed and across the direction of movement of the stop, making the stop movable from the drive roller under pressure of an article engaged by the drive roller and forced against the inclined surface.

2. A device adapted to separate and feed thin pliant paper sheets from a stack and, when in upright position, comprising: a frame, a friction surfaced drive roller horizontally rotatably fixed to the frame, a support table attached to the frame and having a flat continuous surface with a length that is at least a substantial fraction of the length of said paper sheets, one end of the table being beneath the drive roller and the table being biased upwardly toward tangency with the drive roller to urge the leading edge portion of the topmost sheet in the stack tangentially against the bottom of the drive roller, and a stop resiliently biased into contact with the bottom of the drive roller adjacent the end of the support table, the stop presenting a barrier surface substantially along a radial plane of the drive roller and the stop being supported by a pair of arms pivotally attached to the frame at a point located below a level slightly above the top of the stop, a portion of the surface of the top of the stop adjoining the area of abutment being inclined away from the roller toward the support table and angled across the path of feed and across the direction of movement of the stop, the stop being movable from the drive roller under pressure of an article engaged by the drive roller and forced against the inclined surface.

3. The device of claim 2 including means for first rotating the drive roller to initiate the separation and feeding of a top sheet from said stack, and then permitting the roller to rotate freely under the influence of said sheet during further withdrawal thereof from the stack.

4. A device adapted to separate and feed thin pliant paper sheets from a stack and, when in upright position, comprising: a frame, a rubber surfaced drive roller horizontally rotatably fixed to the frame, means for first rotating the drive roller and then permitting it to rotate freely, a support table having a fiat continuous surface with a length that is at least a substantial fraction of the length of said paper sheets, one end of the table being pivotally attached to the frame, the other end being beneath the drive roller and being biased upwardly toward tangency with the drive roller to urge the topmost sheet in the stack tangentially against the bottom of the drive roller, and a stop resiliently biased into contact with the bottom of the drive roller adjacent the end of the support table, the stop presenting a barrier surface substantially along a radius of the drive roller and being supported by a pair of arms pivotally attached to the frame at a point located below a level slightly above the top of the stop, the abutting portion of the surface of the :top of the stop being fiat and tangential to the roller, and a portion adjoining -the fiat surface of abutment being inclined away from the roller toward the table and angled across the path of feed and across the direction of movement of the 10 stop, the stop being movable from the drive roller under pressure of an article engaged by the drive roller and forced against the inclined surface.

References Cited by the Examiner UNITED STATES PATENTS 390,277 10/1888 Allen 27139 496,872 5/1893 Ethridge 27139 625,861 5/1899 Vail et a1. 27143 X 694,850 3/1902 French 271-43 X 1,596,056 8/1926 Mader 27141 2,705,636 4/1955 La Bombard 271--36 3,194,553 7/1965 Larsson 27141 M. HENSON WOOD, JR., Primary Examiner. W. MCCARTHY, A. KNOWLES, Assistant Examiners. 

1. A DEVICE FOR SEPARATING AND FEEDING SHEET-TYPE ARTICLES FROM A STACK COMPRISING A FRAME, A DRIVE ROLLER ROTATABLY FIXED TO THE FRAME, VERTICALLY MOVABLE SUPPORT MEANS FOR THE STACK ATTACHED TO THE FRAME, AN END OF THE SUPPORT MEANS BEING POSITIONED BENEATH AND BIASED TOWARD THE DRIVE ROLLER TO URGE THE LEADING EDGE OF THE TOPMOST ARTICLE OF THE STACK TANGENTIALLY AGAINST THE BOTTOM OF THE DRIVE ROLLE, AND A STOP REWILIENTLY BIASED INTO CONTACT WITH THE BOTTOM OF THE DRIVE ROLLER ADJACENT SAID END OF THE SUPPORT MEANS, MOVABLE FROM THE ROLLER IN A DIRECTION ANGLED TO THE PATH OF FEED, AND SUPPORTED BY A PAIR OF ARMS PIVOTALLY ATTACHED TO THE FRAME BELOW A LEVEL SLIGHTLY ABOVE THE TOP OF THE STOP, THE SURFACE OF THE TOP OF THE STOP INCLUDING A PORTION ADJOINING THE AREA OF ABUTMENT INCLINED AWAY FROM THE ROLLER TOWARD THE SUPPORT MEANS AND ANGLED ACROSS THE PATH OF FEED AND ACROSS THE DIRECTION OF MOVEMENT OF THE STOP, MAKING THE STOP MOVABLE FROM A DRIVE ROLLER UNDER PRESSURE OF AN ARTICLE ENGAGED BY THE DRIVE ROLLER AND FORCED AGAINST THE INCLINED SURFACE. 